[UI] Create an "ExportsHub" API and move exports popover to header. #5795
Description
Describe the issue
In the Statements view, we have the ability to export the SQL result in a csv. We show the progress and download button in a popover called "Exports".
Now we have exporting functionality in a few different places and there is a need for a global "Exports" popover.
It must be placed in the shell header.
Therefore we will also need a new "ExportsHub" API similar to the NotificationHub API.